It may be desirable to form a patterned layer of platinum-containing metal in a microelectronic device. Etching platinum-containing metal is difficult. Wet etching requires very strong acids such as aqua regia, and results in platinum-containing residue in the etched areas. Moreover, wet etching tends to be non-uniform, requiring significant overetch, which introduces unwanted variation in lateral dimensions of the patterned layer. Dry etching may be accomplished by sputter etching, also referred to as ion milling, but results in undesired redeposited platinum-containing material on the microelectronic device, which may reduce reliability of the microelectronic device. Furthermore, sputter etching may result in depositing unwanted platinum containing residue on interior surfaces of the sputter etching chamber, which may cause contamination on subsequently processed wafers. Sputter etching also has poor selectivity to materials in layers under the platinum-containing metal.